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static inline int
dec_loop_avx2_inner (const uint8_t **s, uint8_t **o, size_t *rounds)
{
const __m256i lut_lo = _mm256_setr_epi8(
0x15, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11,
0x11, 0x11, 0x13, 0x1A, 0x1B, 0x1B, 0x1B, 0x1A,
0x15, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11,
0x11, 0x11, 0x13, 0x1A, 0x1B, 0x1B, 0x1B, 0x1A);
const __m256i lut_hi = _mm256_setr_epi8(
0x10, 0x10, 0x01, 0x02, 0x04, 0x08, 0x04, 0x08,
0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10,
0x10, 0x10, 0x01, 0x02, 0x04, 0x08, 0x04, 0x08,
0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10);
const __m256i lut_roll = _mm256_setr_epi8(
0, 16, 19, 4, -65, -65, -71, -71,
0, 0, 0, 0, 0, 0, 0, 0,
0, 16, 19, 4, -65, -65, -71, -71,
0, 0, 0, 0, 0, 0, 0, 0);
const __m256i mask_2F = _mm256_set1_epi8(0x2F);
// Load input:
__m256i str = _mm256_loadu_si256((__m256i *) *s);
// See the SSSE3 decoder for an explanation of the algorithm.
const __m256i hi_nibbles = _mm256_and_si256(_mm256_srli_epi32(str, 4), mask_2F);
const __m256i lo_nibbles = _mm256_and_si256(str, mask_2F);
const __m256i hi = _mm256_shuffle_epi8(lut_hi, hi_nibbles);
const __m256i lo = _mm256_shuffle_epi8(lut_lo, lo_nibbles);
if (!_mm256_testz_si256(lo, hi)) {
return 0;
}
const __m256i eq_2F = _mm256_cmpeq_epi8(str, mask_2F);
const __m256i roll = _mm256_shuffle_epi8(lut_roll, _mm256_add_epi8(eq_2F, hi_nibbles));
// Now simply add the delta values to the input:
str = _mm256_add_epi8(str, roll);
// Reshuffle the input to packed 12-byte output format:
str = dec_reshuffle(str);
// Store the output:
_mm256_storeu_si256((__m256i *) *o, str);
*s += 32;
*o += 24;
*rounds -= 1;
return 1;
}
static inline void
dec_loop_avx2 (const uint8_t **s, size_t *slen, uint8_t **o, size_t *olen)
{
if (*slen < 45) {
return;
}
// Process blocks of 32 bytes per round. Because 8 extra zero bytes are
// written after the output, ensure that there will be at least 13
// bytes of input data left to cover the gap. (11 data bytes and up to
// two end-of-string markers.)
size_t rounds = (*slen - 13) / 32;
*slen -= rounds * 32; // 32 bytes consumed per round
*olen += rounds * 24; // 24 bytes produced per round
do {
if (rounds >= 8) {
if (dec_loop_avx2_inner(s, o, &rounds) &&
dec_loop_avx2_inner(s, o, &rounds) &&
dec_loop_avx2_inner(s, o, &rounds) &&
dec_loop_avx2_inner(s, o, &rounds) &&
dec_loop_avx2_inner(s, o, &rounds) &&
dec_loop_avx2_inner(s, o, &rounds) &&
dec_loop_avx2_inner(s, o, &rounds) &&
dec_loop_avx2_inner(s, o, &rounds)) {
continue;
}
break;
}
if (rounds >= 4) {
if (dec_loop_avx2_inner(s, o, &rounds) &&
dec_loop_avx2_inner(s, o, &rounds) &&
dec_loop_avx2_inner(s, o, &rounds) &&
dec_loop_avx2_inner(s, o, &rounds)) {
continue;
}
break;
}
if (rounds >= 2) {
if (dec_loop_avx2_inner(s, o, &rounds) &&
dec_loop_avx2_inner(s, o, &rounds)) {
continue;
}
break;
}
dec_loop_avx2_inner(s, o, &rounds);
break;
} while (rounds > 0);
// Adjust for any rounds that were skipped:
*slen += rounds * 32;
*olen -= rounds * 24;
}
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